You are not cannon fodder on the front lines if there is not a war going on. They move there during the Long Peace. And yes, in the end, they *do* get wiped out there. Barahir's band is killed, leaving Beren as the sole survivor and Dorthonion empty. Presumably, they move to Dorthonion because they want to be there, in a more 'active' place than they were safely tucked away in Nargothrond.
How many generations do you think it would take to transform them from a people living in peace to a people ready for fighting? With the understanding that they have been training with Elves in both Nargothrond and Dorthonion all along?
Timeline considerations:
At the moment, here are the order of events that we would be telling in our story:
- Bëor meets Finrod
- Bëor's people move to Nargothrond
- Haleth at the Stockade
- Haleth's people move to Brethil
- Council.
- Bereg's people go east. Amlach goes to Himring. Hador's people go to Dor-lomin.
- Adanel and young Andreth get the House of Bëor to move to Dorthonion (Ladros)
I'm not clear on where, exactly, the death of Bëor needs to fall in the story, but before the Council, certainly. The desire to push Andreth earlier into the timeline (and keep her on screen as long as possible) suggests that we'll keep her as Barahir's aunt rather than as his older sister. So, at this point, we have a full two generations being born and growing up in Dorthonion prior to the Dagor Bragollach. Is that sufficient, do you think?